The present invention relates generally to computer networks and communication systems, and more specifically to a system and a method for extending the address resolution protocol (ARP) for use in Internet Protocol (IP) Virtual Networks.
A Virtual Network is an allocation of networking resources that enables independent networking operation over a physical network of devices on which it is configured. In other words, a Virtual Network may be configured over a core set of networking devices, such as devices commonly referred to as switches and/or routers, to enable a geographically distributed group of hosts to interact and be managed as a single logical network. Some Virtual Networks are referred to as Virtual Private Networks (VPNs). The “private” aspect of a Virtual Network may refer to the use of procedures to ensure secure communications over the Virtual Network, by providing confidentiality, message integrity and authentication among participating users and hosts. Virtual Networks may also be private in the sense that they are accessible only to associated sets of users. Accordingly, any Virtual Network with controlled access may be considered a Virtual Private Network. Various existing carrier services provide such controlled access Virtual Networks, including Multi-Protocol Label Switching (MPLS) based services.
As it is generally known, MPLS integrates what is generally referred to as “Layer 2 information” describing individual network links in terms of their bandwidth, latency, and/or utilization, into the Internet Protocol (IP) Layer 3 of an autonomous network, such as a router core operated by an Internet Service Provider (ISP). When packets enter an MPLS-based network, Label Edge Routers (LERs) give them a label (identifier). These labels not only contain information based on the routing table entry associated with the received packet, (i.e., destination, bandwidth, delay, and other metrics), but also refer to the source IP address, Layer 4 socket number information, and differentiated service attributes. Once this classification is complete and mapped, different packets are assigned to corresponding Labeled Switch Paths (LSPs), in which Label Switch Routers (LSRs) place outgoing labels on the packets. By use of these LSPs, network operators can divert and route traffic based on data-stream type and Internet-access customer, thus effectively creating a limited access Virtual Network.
In various types of Virtual Networks, including MPLS provided Virtual Networks, an independent, associated IP address space may be associated with each Virtual Network. Such a Virtual Network may be referred to as a Virtual IP Network. For the purposes herein, the term Virtual Networking Device (VND) will be used to refer to a networking device capable of simultaneously handling traffic on multiple Virtual IP Networks.
As it is generally known, the Address Resolution Protocol (ARP), as defined in Request for Comments (RFC) 826, provides mappings between IP addresses and Ethernet (MAC) addresses within a network. As it is generally known, IP addresses are layer 3 addresses in the Open Systems Interconnection (OSI) model. Layer 3 addresses are also referred to as Network layer addresses. The Network layer is concerned with knowing the address of the neighboring nodes in the network and selecting routes through the network. Routers are typically considered to be layer 3 devices, and the routing of packets through a network is often based on layer 3 addresses contained within packets.
In existing systems, when a router wishes to send data to another device connected via Ethernet or Gigabit Ethernet link, it issues an ARP request containing the IP address of that device. The ARP request is then broadcast to all devices on a shared physical link to which the router is connected. The destination device, seeing its own IP address in the request, then responds with an ARP reply containing its own Ethernet address. The original sender can then store the mapping of the IP address to the Ethernet address internally and use it to generate Ethernet headers for outgoing data traffic having that IP address as a destination address. This approach breaks down when devices are capable of being connected to multiple Virtual IP Networks at the same time, since hosts on separate Virtual Networks that share a physical link may both wish to use the same IP address.
It would therefore be desirable to have a system for translating IP addresses to Ethernet/MAC addresses that operates correctly in the case where a networking device is connected to multiple Virtual IP Networks.